Because loneliness is a phenomenon of concern to nursing, the two long-term objectives of this research are to develop scientifically-based nursing interventions for loneliness in early adolescents that will be tested using an experimental design, and to design a longitudinal panel study that will provide a comprehensive picture of the causes, consequences, and patterns of loneliness during adolescence. The specific aims of the present research are to test alternate explanation of loneliness by Weiss (1973), consequences of loneliness, specifically introspectiveness and health status, and patterns of loneliness using a cross-sectional research design with three distinct samples of early, middle, and late adolescents. A correlational research design suggested by Spector (1981) will be used which requires an interval of time between measuring presume causes and presumed effects. Sampling will take place in public school systems and testing will involve the completion of twelve self-report instruments, eleven of which have reliability and validity data for adolescents. Psychometric properties for adolescents will be assessed for on instrument. A variety of statistical procedures will be used relative to each specific aim. Alternate explanations (causes) of loneliness will be tested using hierarchical analysis of sets for each sample. consequences of loneliness, specifically introspectiveness and health status, will be tested using correlational and three-variable analysis for each sample. Loneliness will be examined according to age and gender using two-way analysis of variance and using data from all three samples in order to determine the patterns of loneliness over the adolescent span of development. Data will be interpreted in light of theory and previous research.